Don't really like the Focus ST - and assuming you're talking about the 2.5/5cyl, I was under the impression the MPG on those was pretty poor.

Golf GTi I hadn't considered, and its a good shout. Few available in the price range, but they're closer to 100k miles. I did drive one when I had the GTA and found them to be pretty dull, but as my options are limited, it's now definately a contender.

I had a 280 (ish) bhp Pumaspeed Focus ST. Averaged 18.5mpg over 6 months, from mixed speeds of driving. My best friend was a business manager for VW at the time the MK5 gti was on the market - he always suggested 25mpg average was what you should expect.

I got an average of 33mpg over 22,000 miles in mine. I checked the fuel computer a few times by brimming the tank and emptying but it turns out that the computer was pretty accurate so I stopped checking.

Octavia vRS, the 2.0 TFSI ones start well below £6k, official combined mpg is 35.8 (although how likely you are to achieve that will be very dependent on how you drive it). Better value than a mkV Golf GTI. Or Seat Leons with the same engine are down at that price now.

Any size/age requirements? Something fun down a B-road or comfy and with pace for longer trips?